The purpose of this study is identifying the differences between '-neunde' and '-nikka', which is a reason connective suffix showing substitution error, to reduce error in using the Korean connective suffix '-neunde'. For this aim, this study aimed to identify that '-neunde' has meaning of [reason] and how [reason] should be suggested by establishing individual meaning of '-neunde' and understanding its original meaning. This study classified the individual meaning of '-neunde' into five categories - [background], [detailed explanation], [concession], [comparison], and [reason] - and proposed that [reason] meaning should be taught after clarifying that the original meaning of '-neunde' is [background].
Previous studies on the differences between '-neunde' and '-nikka' stated that '-neunde' has soft and courteous feeling since it delivers reason implicitly and -'nikka' gives stiff and less courteous feeling since it conveys reason directly. However, this study tried to identify the differences between the two categories based on information structure theory after assuming that existing explanations are poor to explain the differences between '-neunde' and '-nikka'. '-neunde' is used when the content which speaker is trying to convey is new information to listener and '-nikka' can be used when it is old information
Next, in order to examine the aspects of '-neunde', which are being taught in the current Korean language education, 10 types of Korean language textbooks were comparatively analyzed. As a result, a number of problems were discovered including all textbooks classified the meaning of '-neunde' differently, the order was different, and grammatical skills and example sentences did not match. In addition, most textbooks did not have additional explanation about [reason] meaning and seldom identified the differences between similar categories. In this regard, this study proposed that Korean language textbooks should suggest the meaning of [reason] with appropriate example sentences. Furthermore, the education directions of reason '-neunde' have been proposed by emphasizing that comparative explanation between similar categories should be explicitly suggested.
This study is meaningful in the sense that it established individual meaning of '-neunde', which had been expressed in diverse manners in previous studies, based on the standard proposed by Evans (2004). Moreover, this study has significant meaning because it focused on examining [reason] meaning which had not stood out in Korean language learning environments and it identified the differences between the two categories from a new perspective to reduce comparison error rate with similar category '-nikka' used by learners. The part which could not be explained by existing discussion due to information structure has been resolved and this study proposed the distinctive point of learners clearly distinguishing the differences between '-neunde' and '-nikka'.